Abstract
Quantifying the variation in emission properties of fluorescent nanodiamonds is important for developing their wide-ranging applicability. Directed self-assembly techniques show promise for positioning nanodiamonds precisely enabling such quantification. Here we show an approach for depositing nanodiamonds in pre-determined arrays which are used to gather statistical information about fluorescent lifetimes. The arrays were created via a layer of photoresist patterned with grids of apertures using electron beam lithography and then drop-cast with nanodiamonds. Electron microscopy revealed a 90% average deposition yield across 3,376 populated array sites, with an average of 20 nanodiamonds per site. Confocal microscopy, optimised for nitrogen vacancy fluorescence collection, revealed a broad distribution of fluorescent lifetimes in agreement with literature. This method for statistically quantifying fluorescent nanoparticles provides a step towards fabrication of hybrid photonic devices for applications from quantum cryptography to sensing.
Highlights
Diamond has long been studied for its remarkable properties including chemical inertness, biocompatibility, transparency from the ultraviolet to the infra-red range, high thermal conductivity and mechanical strength[1,2,3,4]
The emission spectrum of the NV− centre is centred around 700 nm and its standard fluorescent lifetime in bulk diamond is ~12 ns; both of these aspects make it attractive for biological imaging because autofluorescence from surrounding media can be avoided with spectral filters and/or time-gating[9, 10]
The NV centre has been presented as a sensor, with changes in the environment giving rise to variations in fluorescence, which is the basis of optically detected magnetic resonance (ODMR) measurements
Summary
Diamond has long been studied for its remarkable properties including chemical inertness, biocompatibility, transparency from the ultraviolet to the infra-red range, high thermal conductivity and mechanical strength[1,2,3,4]. Detection of individual colour centres by confocal microscopy was demonstrated 20 years ago[5], and over 500 active optical centres have so far been characterised[6], many of which show single photon emission characteristics[7]. The emission spectrum of the NV− centre is centred around 700 nm and its standard fluorescent lifetime in bulk diamond is ~12 ns; both of these aspects make it attractive for biological imaging because autofluorescence from surrounding media can be avoided with spectral filters and/or time-gating[9, 10]. We present a method for positioning as-received ball-milled nanodiamonds in pre-determined locations on glass, and use it as a tool for measuring the fluorescent lifetime statistics of the deposited material. A number of approaches to locate NV centres in diamond have been developed over the last several years which fall into two broad categories: top-down direct-write techniques, and bottom-up assembly techniques
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